Peristaltic pump having rotatory play

ABSTRACT

A peristaltic pump for an apparatus for extracorporeal blood treatment, especially for a dialysis machine, for conveying fluid in the apparatus is disclosed. The peristaltic pump includes a rotor driven by a drive shaft, the rotor interacting with an elastically deformable fluid line so as to form a cross-sectional constriction which is displaced along the fluid line for conveying fluid by rotation of the rotor, wherein the rotor is coupled to the drive shaft by a coupling structure so as to transmit a torque, wherein the coupling structure couples the rotor and the drive shaft with a play in the direction of rotation relative to each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to German application DE 10 2016 114959.4 filed Aug. 11, 2016, the contents of such application beingincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a peristaltic pump for an apparatus forextracorporeal blood treatment, especially for a dialysis machine, forconveying fluid in the apparatus, the peristaltic pump including a rotorbeing driven to rotate by a drive shaft which interacts with anelastically/flexibly deformable fluid line to form a cross-sectionalconstriction, wherein the cross-sectional constriction is displaced(moved) along the fluid line by rotation of the rotor for conveyingfluid and wherein the rotor is coupled to the drive shaft with acoupling structure so as to transmit a torque. Furthermore, theinvention relates to an apparatus for extracorporeal blood treatmentcomprising a peristaltic pump according to aspects of the invention,especially a dialysis machine, comprising said peristaltic pump.

BACKGROUND OF THE INVENTION

In an apparatus for extracorporeal blood treatment, for example in adialysis machine, it is the function of a peristaltic pump to convey adefined volume of a medium, such as blood or dialysis solution, bydeforming and pinching off an elastically deformable fluid line from anegative pressure side (low-pressure side) to a positive pressure side(high-pressure side). Known peristaltic pumps in said medicalapparatuses usually comprise a rotor, a pump casing and the elastic tubeline disposed between the rotor and the pump casing as a fluid line. Therotor is coupled to a drive axle of the machine with a fixed torque, isdriven by said drive axis and supports pressing elements, e.g. in theform of pressing rollers, adapted to be positioned in the radialdirection and being biased against the tube line and the pump casing bycompression springs.

DESCRIPTION OF THE RELATED ART

Such pump in which pressing rollers are biased radially outwardly withleaf springs is known, for example, from U.S. Pat. No. 3,737,256. Inthis pump, the rotor is connected to a drive axle via a couplingmechanism and is secured to the same in the axial direction with ascrew. A drawback of this pump resides in the fact that the rotor can bereleased/replaced with the aid of a screwing tool only and withcorresponding expenditure of time.

From WO 97/28368 A2 a peristaltic pump for a dialysis machine is knownin which pressing rollers of a rotor biased radially outwardly withspiral springs interact with a pinch line. The rotor has a centralreceiving opening for a drive shaft of a drive motor and is coupled onthe same with a pivoting handle which positively interacts with thedrive shaft. The handle can be pivoted, on the one hand, into a couplingposition in which it positively interacts with the drive shaft and, onthe other hand, into an actuating position in which it is uncoupled fromthe drive shaft and forms a kind of crank for manual actuation of therotor.

From U.S. Pat. No. 4,527,323 a peristaltic pump for a dialysis machineis known the rotor of which is configured similarly to that of U.S. Pat.No. 3,737,256 and with a journal is axially pushed into a slit of adrive axle so as to couple the rotor to the drive axle. The patentfurther discloses a handle adapted to be attached to the rotor formanual mounting or actuation of the rotor.

In known systems and especially in the afore-described pumps it is ageneral drawback that an increased stress of the drive components andthus increased wear may occur for pumps, when load changes or even loadreversals occur during operation. This may especially be the case whenthe rotor is releasably connected or connectable to a drive axle, forexample with radial form closure or force closure. Load changes or loadreversals of this type may occur due to application and may result invarying or even changing strain of components of the drive, for exampleby load or torque reversal. A by-product of such load variations may bean increased noise emission.

In particular, such load variations may occur in peristaltic tube pumpsin which, due to construction, there are always a run-in area and arun-out area which are generally referred to as run-in geometry andrun-out geometry. The run-in area and the run-out area are due to thefact that the inserted tube system of the extracorporeal bloodcirculation has an open pump tube segment and it is not a fully closedtube segment. Therefore, the rotor is in engagement with the tubesegment only via a particular angular range and pinches said tubesegment in interaction with the pump casing, while in a remainingangular range outside the engagement it is released from the tubesegment. Between the two angular ranges there is located the run-inportion in which the rotor engages in the tube segment and,respectively, the run-out portion in which the rotor disengages from thetube segment. When the rotor runs out of the run-out geometry, a shorttorque variation or even a torque reversal occurs, as the compressionspring of the rotor required for compressing the pump segment/tubesegment exploits the radial play newly formed during run-out fordecompression and allows the rotor to advance relative to the rotationof the drive shaft (in addition to the speed thereof) until the driveshaft has caught up with the play again. Due to tolerances between thedrive shaft and the coupling structure of the rotor interacting with theformer, undesired detrimental transmissions of load on tooth flanks ofthe gear unit and disadvantageous and undesired acoustic effects mayoccur in this way.

SUMMARY OF THE INVENTION

Starting from the afore-described state of the art, an object underlyingthe present invention is to eliminate the afore-listed drawbacks,especially to provide a peristaltic pump for an apparatus forextracorporeal blood treatment, especially for a dialysis machine, whichexhibits higher wear resistance and lower noise strain.

In accordance with the present invention, this object is achieved by aperistaltic pump for an apparatus for extracorporeal blood treatment,especially for a dialysis machine, for conveying fluid in the apparatus,wherein the peristaltic pump includes a rotor driven to rotate by adrive axle or drive shaft which interacts with an elastically/flexiblydeformable fluid line to form a cross-sectional constriction which ismoved along the fluid line for conveying fluid by rotation of the rotor,the rotor being coupled to the drive shaft or drive axle with a couplingstructure (coupling) so as to transmit a torque, wherein the couplingstructure couples the rotor and the drive shaft having a play in thedirection of rotation toward each other.

Moreover, an object is achieved by an apparatus for extracorporeal bloodtreatment by a peristaltic pump according to aspects of the invention,especially as disclosed in the present description or as claimed by theattached claims.

The present subject matter of the invention can also be defined so thatthe invention consists in an increase in the radial degrees of freedomof a radial locking element (as component of the coupling structureaccording to aspects of the invention), thus causing undesired negativeload transmission to the drive shaft and tooth flanks of an upstreamgear unit interacting therewith which is present in known pumps to bereduced/prevented. Furthermore, acoustic effects occurring in knownpumps (clicking) which are caused by load variations/torque variationsupon passing the run-in and/or run-out area can be reduced and animproved service life of the gearing can be achieved by the invention.

The coupling structure facilitates sort of “free-wheeling” within anangular range defined by the coupling structure due to its geometry.Said angular range may have been established especially empirically. Theselected/empirically established angular range usually is dependent onthe design and the material properties of the individual functionalelements of the peristaltic pump such as (namely) the rotor and thedrive shaft, as well as on correspondingly applied/defined operatingparameters (e.g. speed of rotation). The play in the direction ofrotation generated by the coupling structure may act, according toaspects of the invention, basically in the run-out area of the rotorfrom the pump segment and/or in the run-in area of the rotor into thepump segment and achieve its effect intended according to aspects of theinvention, respectively.

As described in the foregoing with respect to the state of the art, inthe run-in area and/or in the run-out area variation or even reversal ofradial forces acting on pressure elements of the rotor (or ofmoments/circumferential forces acting on the rotor) may occur whichmight also affect the drive shaft and a drive train operativelyconnected to the latter (gearing). Upon run-out of the rotor, especiallya pressing element interacting with the fluid line (fluid linesupporting structure), from the portion pinching the fluid line, forexample an additional torque may be caused especially in the directionof rotation. This would have to be absorbed and compensated by the driveshaft and thus would have a negative effect as regards acousticemissions (clicking noise) and load of the drive shaft and the gearingsthereof. The play of the coupling structure provided according toaspects of the invention may compensate for or at least reduce suchvariations by the fact that the rotor may have relative advance andrelative overrun with respect to the drive shaft. Despite the providedplay, the rotor and the drive shaft are coupled to each other so as totransmit a torque.

By the free-wheeling function according to aspects of the invention (dueto the play of the coupling structure acting in the direction ofrotation) especially also a two-sided direction of rotation (forward andbackward) may be realized. Moreover, the rotor may be positioned to belargely free, which is required/advantageous for example within thescope of inserting and removing the fluid line, especially within thescope of an automatic threading and unthreading function of the fluidline. At the same time, undesired negative load transmissions to toothflanks of a gearing operatively connected to the drive shaft or of agear unit can even be completely eliminated. Acoustic impacts can bedefinitely reduced as compared to the state of the art. In total, theinvention has a positive influence on the service life of the gearing.On principle, the invention is applicable to almost all knownperistaltic pumps, no matter whether the rotor and the drive shaft arecoupled to each other in a fixed or releasable manner. Moreover, it isapplicable in the case of form closure, force closure as well asmaterial closure between the rotor and the drive shaft.

The peristaltic pump of the apparatus according to aspects of theinvention may convey a defined volume of a medium such as blood ordialysis solution in a common way from a low-pressure side, usually thearterial side, to a high-pressure side, usually the venous side. Theelastic fluid line is inserted into the same formed between the rotorand the support surface formed by the support surface module in loopshape. It may be guided or retained especially by the casing module. Therotor and the supporting surface supporting the elastic fluid line areconfigured and adapted to each other so that a conveying distance isformed therebetween. In the course thereof, the elastically deformablefluid line is deformed and pinched off upon rotation of the rotor aboutthe rotor shaft. The rotor is configured so that the fluid line ispinched only locally or in portions. For example, it may include pinchelements biased against the fluid line and/or adapted to be positionedrelative to the rotor shaft. The pinching point caused by contact withthe rotor moves along with the rotating rotor and is so-to-speak movedthrough the fluid line from the low-pressure side to the high-pressureside. As a consequence, fluid is forced out of the fluid line in theconveying direction. Resupplied fluid is sucked into the line by lowpressure, especially vacuum, forming due to elastic re-formation of thefluid line after deformation by the rotor. The elastically deformablefluid line may be a tube, for example.

By the invention especially the following advantages can be achieved:

By the (angularly/peripherally limited) free-wheeling function in theform closure of the coupling structure the requirements to a two-sideddirection of rotation can be maintained;

undesired negative load transmissions especially to the tooth flanks ofan (upstream) gearing unit can be (completely) eliminated;

acoustic influences are (definitely) reduced by the integratedfree-wheeling function;

the service life of the gearing can be positively influenced;

definitely quieter treatment of patients is possible;

less wear is detected at the gearing.

Advantageous embodiments of the invention are claimed in the subclaimsand shall be illustrated hereinafter.

One embodiment of the peristaltic pump is wherein the rotor and thedrive shaft are removably coupled to each other. This facilitatesespecially easy cleaning and maintenance of the pump. Moreover, thefluid line can be easily replaced.

Preferably, the coupling structure may have at least one flat firstguiding contour formed in parallel to the axis of rotation. Said firstguiding contour may be formed either on the rotor side or on the driveshaft side. It may be especially in the form of a guiding surface, forexample in the form of a flat guiding surface. Such guiding surface canbe configured especially simply by flattening the drive shaft just inparallel to the axis of rotation thereof, for example. It is ofparticular advantage when the coupling structure includes two flat firstguiding contours parallel to each other on diametrically opposed sidesof the axis of rotation. This allows for uniform torque transmission,especially in the case of alternating directions of rotation.

According to another embodiment of the invention, the coupling structureincludes at least a second guiding contour. It is formed and intendedfor interaction with the first guiding contour of the couplingstructure. It may be formed especially of at least two guiding surfacesbeing arranged in parallel to the axis of rotation and inclined relativeto each other. Also the second guiding contour may be provided on thedrive shaft side or on the rotor side. When the first guiding contour isformed on the rotor side, for example, the second guiding contour isformed on the drive shaft side and vice versa. The first and secondguiding contours cause the transmission of the torque between the driveshaft and the rotor.

According to a further embodiment of the invention, the second guidingcontour may be rounded in the transition between the two guidingsurfaces thereof. Alternatively, the first guiding contour may berounded in this way. The radius of such rounding may range from about 5mm to about 25 mm, more preferred from about 10 mm to about 20 mm, evenmore preferred about 15 mm. Such rounded geometry facilitates anespecially smooth transition between the advance and the overrun in thecase of load change in the area of the play provided by the couplingstructure. The first guiding contour may so-to-speak roll off the radiusof the second guiding contour during relative rotation within the playrange and may smoothly change from a first relative position (e.g.synchronous run) to a second relative position (e.g. advance). As aresult, this permits smooth re-engagement of the drive shaft in a torqueclosure with the coupling structure and thus with the rotor. It is ofspecial advantage when the coupling structure according to an embodimentof the invention includes two second guiding contours of this type ondiametrically opposed sides of the axis of rotation.

A similar effect and advantages may be achieved by the second guidingcontour being configured to be rounded in portions or else completely.The rounding extends especially in parallel to the axis of rotation. Itsradius may preferably be within a range of from 5 mm to about 25 mm,more preferred from about 10 mm to about 20 mm or even more preferredabout 15 mm. It is of particular advantage when the coupling structureaccording to an embodiment of the invention includes two second guidingcontours of this type on diametrically opposed sides of the axis ofrotation.

The first and second guiding contour(s) may be configured especiallysimply in that, according to a further embodiment of the invention, thedrive shaft or the rotor has a central groove or is flattened on bothsides. This is robust, easy to manufacture and may especially easilyallow for dismounting the rotor from the drive shaft.

One embodiment of the invention is wherein the rotor can be coupled tothe drive shaft with a locking element or includes the locking element,wherein the first guiding contour or the second guiding contour (and,respectively the first guiding contours or the second guiding contours)are formed on the locking element. The latch element may serve, on theone hand, for forming a torque closure between the rotor and the driveshaft. On the other hand, it may serve for locking the rotor in acondition positioned on the drive shaft so that inadvertent release ofthe rotor during treatment can be excluded.

The locking element may especially be arranged about a pivot axistransversely to the axis of rotation to be pivotal on the rotor. It maybe adapted to be positioned into a locking position coupling the rotorand the drive shaft via the coupling structure to each other and into anunlocking position uncoupling the rotor from the drive shaft. For a pumpincluding such quick acting lock element it is advantageous that therotor can be manually released/replaced with little expenditure of timewithout the aid of a tool/screwing tool. The locking element mayinteract with the rotor especially in the unlocking position such thatit may be used as a handle for manual actuation and for manual drive ofthe rotor, respectively. This is especially advantageous in the case ofpower breakdowns to be able to ensure continuous pump function. In theunlocking position, the rotor may be uncoupled from the drive shaft sothat, for example, the fluid line may be replaced and/or the pump iseasily accessible for cleaning.

It can also be stated that the invention relates to a functionallyintegrated locking element of a releasable positive-locking shaft-hubconnection of a rotor to a drive shaft for the rotor. The rotor and,where necessary, the drive shaft may be components of a peristalticroller pump, especially a tube pump for medical engineering the intendedapplication of which may be found especially in extracorporeal bloodtreatment. The rotor allows, together with the elastic materialproperties of the pump segment which is inserted against a cylindricalrunning surface of the pump casing in loop shape, a pumping functionthat ensures blood delivery to a dialyzer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawings. Included in thedrawings are the following figures:

FIG. 1 shows a schematic representation of a cutout of an apparatus forextracorporeal blood treatment.

FIG. 2 shows a top view onto a locking element comprising a couplingstructure according to aspects of the invention.

FIG. 3 shows another top view onto the locking element of FIG. 2.

FIG. 4 shows an enlarged cutout of a coupling structure according toaspects of the invention.

FIG. 5 shows a bottom view of a rotor comprising a coupling structureaccording to aspects of the invention in a first operating condition.

FIG. 6 shows a bottom view of the rotor in a second operating conditionand

FIG. 7 shows a bottom view of the rotor in a third operating condition.

FIG. 8 illustrates an example of how the rotor engages the drive shaftby way of the intervening locking element structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 exemplifies a cutout of an apparatus for extracorporeal bloodtreatment according to aspects of the invention. There is substantiallyshown the entire extracorporeal blood circulation of the apparatus. Itincludes an arterial blood line 1 with which blood is guided from apatient (not shown) to a peristaltic pump 2 of modular design of thetreatment apparatus. Upstream of the peristaltic pump 2 an arterialpressure sensor 3 is provided by which the pressure upstream of theperistaltic pump 2, i.e. the low-pressure side pressure is measured. Onthe high-pressure side of the peristaltic pump 2 a high-pressure bloodline 4 leads to an arterial blood collector 5. Directly at the outlet ofthe peristaltic pump 2, additive may be supplied with a feed line 6 anda pump 7 to the blood present in the system, e.g. heparin forhemodilution.

From the arterial blood collector 5 a line 8 guides blood which is underhigh pressure but is untreated yet and loaded with waste materials to adialyzer 9. On the inlet side, dialysis solution is supplied thereto viaa dialysis solution feed line 10. In the dialyzer 9 blood is treated,e.g. purified in a known manner with the dialysis solution. Useddialysis solution is removed from the dialyzer 9 via a dialysis solutiondrain 11 and is supplied to waste disposal or recycling (not shown).Treated blood is guided with blood drain 12 from the dialyzer 9 to avenous air collector 13 where air is separated with an air trap 14. Atthe venous air collector 13 a venous pressure sensor 15 is provided bywhich the venous pressure, namely the high-pressure side pressure, isdetected. Treated blood is returned from the air trap 14 via a venousblood line 16 to the patient. In FIG. 1 also a unit 17 for monitoringand controlling the apparatus is shown. The apparatus for extracorporealblood treatment is encapsulated by a housing 100 which is configured atleast in part as a formed sheet metal part.

The peristaltic pump 2 includes a rotor 18 indicated in FIG. 1 and anequally indicated pump casing 19 having a guiding surface. Between therotor 18 and the guiding surface of the pump casing 19 an elasticallydeformable fluid line 20 is arranged which is connected, on the inletside, to the arterial blood line 1 and, on the outlet side, to thehigh-pressure blood line 4. The fluid line 20 is deformed and pinched bythe effect of the rotor 18 between the same and the guiding surface ofthe pump casing 19 so that fluid delivery from the arterial blood line 1to the high-pressure blood line 4 is brought about.

FIG. 2 illustrates a locking element 21 for locking the rotor 18 on adrive shaft 22 of the dialysis machine visible in the FIGS. 4 to 7. Thelocking element 21 includes a pivoted tab 23 by which it can bepivotally fixed to the rotor 18. A recess whose walls are formingrespective second guide contours 24, 25 in accordance with the inventionis configured in the locking element 21.

The FIGS. 5 to 7 illustrate the second guiding contours 24, 25 of thelocking element 21 in mesh with the drive shaft 22. The latter isconfigured to be flattened on both sides in parallel with its axis ofrotation and includes two first guiding contours in the form offlattened portions or guiding planes 26, 27 which are diametricallyopposed to each other. Said guiding planes 26, 27 are flat andconfigured in parallel to each other. In contrast to this, the guidingcontours 24, 25 of the first guiding contour are configured to berounded having a first radius R1 and a second radius R2. According toaspects of the invention, the first radius may be from about 5 mm toabout 25 mm, more preferred about from 10 mm to about 20 mm, even morepreferred about 15 mm. The second radius preferably is about 3 mm. InFIGS. 5 to 7 furthermore pressing rollers 29, 30 of the rotor 18 areillustrated which interact with the fluid line 20 and pinch the same forconveying fluid therethrough. Each of the pressing rollers 29, 30 isrotatably supported on a corresponding pivoted arm 31 and 32,respectively, being biased by a compression spring 33, 34 so as tocontact the fluid line 20. Each of the pivoted arms 31, 32 is pivotingabout a pivot axis 35, 36. FIG. 8 illustrates how a portion 800 of thelocking element of FIG. 3 fits in the rotor 18 to engage the drive shaft22.

Unless either of the pressing rollers 29, 30 is in pinching engagementwith the fluid line 20, the pivoted arm 31 and 32, respectively, thereofis pivoted outwards, i.e. away from the drive shaft 22, by the action ofthe respective compression spring 33, 34. In the run-in area therespective pressing roller 29, 30 enters into contact with the fluidline 20 and, due to the distance between the pressing roller 29, 30 fromthe supporting surface decreasing during continuous rotation, is pivotedinwards in the direction of the drive shaft 22. After passing the run-inportion the respective pressing roller 29, 30 is provided in theconveying portion of the fluid line 20 and pinches the same so as toconvey fluid. After passing the conveying portion the respectivepressing roller 29, 30 enters into the run-out portion and, when passingthe same, the radial distance of the pressing roller 29, 30 from theguiding surface increases again and the corresponding pivoted arm 31, 32pivots outward again (away from the drive shaft 22) due to thedecreasing pressure exerted by the fluid line 20. The maximum relativepivot angle α between the rotor 18 and the drive shaft 22 given withmaximum advance is inserted in FIG. 7.

FIG. 4 illustrates in a magnification that between the rounded guidingcontours 24, 25 of the second guiding contour and the flat guidingsurfaces of the first guiding contour a gap 28 providing play in thedirection of rotation is formed. It can be clearly inferred that thefirst guiding contour 26, 27 may roll off the second guiding contours24, 25 upon rotation of the rotor 18 relative to the drive shaft 22.Said roll-off process or the relative rotation between the rotor 18 andthe drive shaft 22 becomes especially clear from a comparison of FIGS.5, 6 and 7. In FIG. 5, an operating condition is shown in which thedrive shaft 22 is in mesh with the rotor 18 in an operating position ora neutral position. Such position is given when none of the two pressingrollers 29, 30 is provided in the run-in area or in the run-out area. Ifeither of the rollers 29, 30 is provided in the area of the pump outlet(where the roller lifts off the fluid line), the rotor 18 is acceleratedby the pressure of the respective compression spring 33, 34 in thedirection of rotation (clockwise in the Figures) and thereforetemporarily rotates more quickly than the driven shaft 22. Thiscondition (advance) is illustrated in FIGS. 6 and 7. Due to the play 28,the afore-described relative positioning between the rotor 18 and thedrive shaft 22 and, consequently, the described variations of loads andmoments are not transmitted to the latter.

The invention claimed is:
 1. A peristaltic pump of an apparatus forextracorporeal blood treatment, the peristaltic pump configured toconvey fluid in the apparatus, the peristaltic pump comprising: a driveshaft; a rotor driven by the drive shaft, the rotor configured to pressan elastically deformable fluid line against a guiding surface of a pumpcasing so as to form a cross-sectional constriction, wherein saidcross-sectional constriction is displaced along the fluid line to conveyfluid by rotation of the rotor, and the pump casing extends partiallyaround a rotation path of the rotor between a run-in portion in whichthe rotor engages the elastically deformable fluid line, and a run-outportion in which the rotor disengages the elastically deformable fluidline; and a coupling structure coupling the rotor to the drive shaft soas to transmit a torque, the coupling structure coupling the rotor andthe drive shaft with play between the coupling structure and the driveshaft in the direction of rotation.
 2. The peristaltic pump according toclaim 1, wherein the rotor and the drive shaft are releasably coupled toeach other.
 3. The peristaltic pump according to claim 1, wherein thecoupling structure includes at least one flat first guiding contourformed parallel to an axis of rotation.
 4. The peristaltic pumpaccording to claim 3, wherein the coupling structure further includestwo flat first guiding contours parallel to each other on diametricallyopposed sides of the axis of rotation.
 5. The peristaltic pump accordingto claim 1, wherein the coupling structure includes at least a secondguiding contour including at least two guiding surfaces which arearranged in parallel to an axis of rotation and inclined relative toeach other.
 6. The peristaltic pump according to claim 5, wherein thesecond guiding contour is at least partially rounded.
 7. The peristalticpump according to claim 6, wherein the second guiding contour has aradius of 5 mm to 25 mm.
 8. The peristaltic pump according to claim 7,wherein the second guiding contour has a radius of 10 mm to 20 mm. 9.The peristaltic pump according to claim 8, wherein the second guidingcontour has a radius of 15 mm.
 10. The peristaltic pump according toclaim 5, wherein the coupling structure includes two second guidingcontours on diametrically opposed sides of the axis of rotation, eachsecond guiding contour including at least two guiding surfaces which arearranged in parallel to the axis of rotation and inclined relative toeach other.
 11. The peristaltic pump according to claim 2, wherein thedrive shaft or the rotor has a central groove or flattened portions ontwo sides.
 12. The peristaltic pump according to claim 1, wherein thecoupling structure comprises a locking element that is movable relativeto the rotor.
 13. The peristaltic pump according to claim 1, wherein thelocking element is adapted to be positioned into a locking positioncoupling the rotor to the drive shaft via the coupling structure andinto an unlocking position uncoupling the rotor from the drive shaft.14. The peristaltic pump according to claim 1, wherein the apparatus isa dialysis machine.